WJEC AS Level Physics Unit 1.1 (Basic Physics)

40 flashcards · Physics · by Lili Lewis

  1. What is a base unit?

    A unit of measurement that all other units are derived from.

  2. What are the 6 essential base units?

    Mass Length Time Amount of Substance Current Temperature

  3. What is Mass measured in?

    Kilograms (Kg)

  4. What is Length measured in?

    Metres (m)

  5. What is Time measured in?

    Seconds (s)

  6. What is Amount of Substance measured in?

    Moles (Mol)

  7. What is Current measured in?

    Amperes (Amps)

  8. What is Temperature measured in?

    Kelvin (K)

  9. What are derived units used for?

    Quantities other than that of the base units such as Force, Power and Resistance.

  10. What are the 8 essential derived units?

    Force Pressure Energy (Work Done) Power Electric Potential Difference (Voltage) Electric Resistance Electric Charge Frequency

  11. How do we derive Force?

    Equation (for derived quantity); F=ma (Force = mass x acceleration) Units; Newtons (N) Units in SI units base; kgms-2 Deriving force; kg x ms-1 = kgms-2

  12. How do we derive Pressure?

    Equation (for derived quantity); P=F/A (Pressure = Force/Area) Units; Pascals (Pa) Units in SI units base; kgm-1s-2 Deriving Pressure; kgms-2/m2 = kgm-1s-2

  13. How do we derive Energy (Work Done)?

    Equation (for derived quantity); E=Fd (Force x displacement) Units; Joules (J) Units in SI units base; kgm2s-2 Deriving Energy (Work Done); kgms-2 x m = kgm2s-2

  14. How do we derive Power?

    Equation (for derived quantity); P=E/t (Energy/time) Units; Watts (W) Units in SI units base; kgm2s-3 Deriving Power; kgm2s-2/s = kgm2s-3

  15. How do we derive Electric Potential Difference (Voltage)?

    Equation (for derived quantity); V=P/I Units; Volts (V) Units in SI units base; kgm2s-3A-1 Deriving Electric Potential Difference (Voltage); kgm2s-3/A = kgm2s-3A-1

  16. How do we derive Electric Resistance?

    Equation (for derived quantity); R=V/I Units; Ohms (Ω) Units in SI units base; kgm2s-3A-2 Deriving Electric Resistance; kgm2s-3A-1/A = kgm2s-3A-2

  17. How do we derive Electric Charge?

    Equation (for derived quantity); Q=It Units; Coulombs (C) Units in SI units base; As Deriving Electric Charge; A/s = As

  18. How do we derive Frequency?

    Equation (for derived quantity?); Rotations per second Units; Hertz (Hz) Units in SI units base; s-1 Deriving Frequency; 1/s = s-1

  19. What is checking an equation for homogeneity?

    Breaking down the equation into its constituent base units to check whether the equation is correct. If the equation is correct it will have the same base units on either side, meaning the equation is homogeneous.

  20. What is a scalar quantity?

    A scalar is a quantity that has magnitude only.

  21. What is a vector quantity?

    A vector is a quantity that has magnitude and direction.

  22. Scalar quantities

    Mass Density Speed Frequency Time Area Volume Pressure Energy Power

  23. Vector quantities

    Velocity Force Acceleration Weight Momentum

  24. Coplanar Vectors

    Vectors with the same direction (plane) as each other.

  25. Adding/subtracting vectors

    Drawing tip to tail Pythagoras Basic Trigonometry (Soh/Cah/Toa)

  26. Resolving a vector in particular directions

    This means finding vectors (the so-called components) in these directions, which add together vectorially to make the original vector, and so, together, are equivalent to this vector.

  27. Resolving perpendicular vectors

    Combine them to form a resultant using Pythagoras.

  28. Resolving a vector

    Splitting a vector into two separate components. E.g. Horizontal and vertical force.

  29. Shortcut for resolving vectors

    When resolving vectors, if the component is next to the angle, it will always be Cos. If it turns away from the angle it is Sin.

  30. Density

    ρ=m/v Units; kgm-3 or gcm-3

  31. Moment of a force

    The moment of a force is called the “turning effect” of a force. If a body is pivoted at some point and a force is applied to the body it will rotate about that point.

  32. Definition of a moment

    A moment is defined as the force x the perpendicular distance between the pivot and the perpendicular distance of the line of action of a force.

  33. Moment equation

    Moment = FD F is the Force (N) D is the perpendicular distance (m) Moment is measured in Nm

  34. Principle of moments

    For a system to be in equilibrium, ∑ anticlockwise moments about a point = ∑ clockwise moments about the same point.

  35. Centre of gravity

    A single point on the body from which the entire weight of the body may be considered to act.

  36. Centre of gravity of a sphere

    Draw a square around it and use the intersection of diagonal lines from each corner.

  37. Centre of a gravity of a cuboid

    Draw diagonal lines from each corner and use the intersection.

  38. Centre of gravity of a cylinder

    Treat it as a 2D shape and draw diagonal lines from each corner. Then use the intersection.

  39. Name one scenario where centre of gravity is useful.

    Toppling angles.

  40. Conditions needed for equilibrium

    The resultant force must be zero. The resultant moment must be zero.